Cellulases are amongst the most widely used enzymes in industry. They are generally applied in textile industry, detergent industry, pulp and paper industry, feed and food industry, including baking, and in hydrolysis of lignocellulosic material for, e.g. bioethanol production etc. The practical use of cellulases is hampered by the nature of the cellulase compositions, which are often enzyme mixtures having a variety of activities and substrate specificities. For this reason, efforts have been made to obtain cellulases having only the desired activities. The unique properties of each cellulase make some more suitable for certain purposes than others.
In fabric treatment cellulases attack the chains of cellulose molecules that form the cotton fibers, thereby affecting the characteristics of the fabric.
In textile industry a “stone washed” or abraded look has been denim producers' interest in recent years. Traditional stone washing with pumice stones reduces the strength of fabric and burdens the laundering apparatuses. The trend has been towards enzymatic denim finishing processes and cellulases have replaced or are being used together with pumice stones to give the fabric its desired “worn” look. Controlled enzyme treatments result in less damage to the garments and machines and eliminate the need for disposal of stones.
Additionally, textile industry uses cellulases in biofinishing, i.e. to create permanent improvement of depilling, and to improve pilling resistance, clear surface structure by reduced fuzz, improve textile handle, such as softness, smoothness and a silkier feel, improve drapability and brighter colors of the textile and improve moisture absorbability.
Cellulases comprise a catalytic domain/core (CD) expressing cellulase activity. In addition to the catalytic domain the cellulase molecule may comprise one or more cellulose binding domains (CBDs), also named as carbohydrate binding domains/modules (CBD/CBM), which can be located either at the N- or C-terminus of the catalytic domain. CBDs have carbohydrate-binding activity and they facilitate the enzymatic action on solid substrates. The catalytic core and the CBD are typically connected via a flexible and highly glycosylated linker region.
Cellulases that attack primarily on the surface of the fiber are especially useful in stone washing of denim dyed with Indigo dye, as the dye is located on the surface of the fiber. Cellulases applied in denim treatment are usually divided into two main groups: acid and neutral cellulases. Acid cellulases typically operate at pH 4.5-5.5 and the neutral cellulases in the range of pH 6-8. When used to treat cotton fabric, acid cellulases generally require a shorter washing time than neutral cellulases. Acid cellulases are especially used in biofinishing (depilling) and also in denim treatment (biostoning). Acid cellulases used in biostoning mainly originate from Trichoderma reesei (sexual form Hypocrea jecorina) and the neutral cellulases come from a variety of fungi, including genera of Melanocarpus, Humicola, Thielavia, Myceliophthora, Fusarium, Acremonium, and Chrysosporium (Haakana et al. 2004). T. reesei enzymes include, e.g., cellulases from the glycoside family 5 (endoglucanase II, EGII), family 7 (cellobiohydrolase I, CBHI) and family 12 (endoglucanase III, EGIII; Ward et al. 1993), and the neutral cellulases, most often endoglucanases, from family 45 and family 7 (Henrissat, 1991; Henrissat and Bairoch, 1993).
The wide spectrum of industrial uses for endoglucanases has established a need for commercial endoglucanase products showing desired performance at desired conditions such as pH and temperature ranges. Acid cellulases classified as EGII and EGIII have been described for use in i.a. textile treatment. For example WO2007/118935 describes the use of Cel5 (EGII) enzymes in textile finishing. EP 586,375 B1 discloses detergent compositions comprising a thoroughly characterized Trichoderma spp. EGIII enzyme with a pH-optimum of 5.5-6.0, pI of 7.2-8.0, and MW of 23-28 kDa. US2007/0026420 describes a method for obtaining genes for novel enzymes, which share certain conserved sequences with EGIII from Trichoderma reesei. Properties of the EGIII like cellulases are not exemplified but a temperature in the range of 35° C. to 65° C. is expected to be suitable for these enzymes.
The majority of the industrially used enzymes work better at elevated temperatures, usually about >50° C., but for energy saving reasons, better color fastness and reduction of shrinkage of garments there is a need for enzymes with good performance at lower temperature levels i.e. <50° C., for example about 30 to 40° C., or even 20 to 40° C. Such cold active enzymes have been described e.g. in bacteria, especially in Bacillus. However, production of bacterial enzymes for industrial applications is complicated and laborious compared to the production of fungal enzymes. Still there is very little knowledge about possible cold active fungal endoglucanases.
Thus there is a continuous need for new and advantageous endoglucanases having desired properties and thermal profiles. The present invention meets this need.